The present invention relates to a filter assembly for use with a commercial air-purifying apparatus. More particularly, it relates to a commercial air filter assembly and associated filtration unit configured to facilitate convenient installation and replacement of the filter assembly.
In recent years, there has been a growing interest to improve environmental air conditions in homes and in commercial settings, such as offices, restaurants, taverns, bowling alleys, hospitals, laboratories, lavatories, and the like. As more information has been made available to the public concerning the hazards of indoor air pollution, there has been an increased demand for air filtration devices that can be used to effectively improve air quality.
With respect to commercial applications, a self-contained, stand-alone air cleaning or filtration unit is normally employed. Stand-alone air filtration units can assume a wide variety of forms, but generally include a housing maintaining one or more applicable filter materials and a fan or blower unit. Alternatively, the blower unit and filter can be formed as separate modules, fluidly connected by ductwork. Regardless, the filtration unit housing (for both self-contained and modular configurations) defines an inlet region, within which the filter(s) is disposed, as well as an outlet or exhaust port. Most commercial settings include a false ceiling, such that the housing is easily "hidden" above the ceiling, with only a grille or air intake opening being visible to persons within the room. During use, the fan or blower unit is operated to draw room air through the filter(s) via the inlet region. The filter material or media removes undesirable air-borne particles and/or odors, such as dust, smoke, pollen, molds, etc., from the air stream. Following interaction with the filter material, the now "cleansed" air is forced, via the blower, back into the room through the outlet. A continuous intake and supply of air preferably generates a desired air re-circulation pattern within the room.
Certain types of filter media, or combinations of different filter media, have been identified as being highly proficient in removing unwanted airborne contaminants. To this end, airborne contaminants are generally categorized as particulate (e.g., pollen, molds, bacteria, smoke, etc.) or gaseous (e.g., odor, carbon monoxide, formaldehyde, volatile organic compounds (VOCs), etc.). A particulate filter is employed to remove airborne fibers or particles, and is typically "rated" according to filtering efficiency and resistance to airflow. For example, a well-known particulate filter is a high efficiency particulate arrestance (HEPA) filter. HEPA filters are generally comprised of intertwined, small (less than 1 micron) glass fibers and have a minimum efficiency of 99.97% relative to 0.3 micron dioctyl phthalate (DOP) particles. Alternatively, the particulate filter may assume other forms (with lower efficiencies), such as cellulose, wool felt or glass fiber filters with efficiencies ranging from 30%-95% ASHREA rated dust spot efficiency. For enhanced filtration of gas molecules and odors (e.g., tobacco smoke odors, cooking odors, VOCs, etc.), a filter incorporating a sorbent material (or "sorbent material filter") is normally employed. A sorbent material filter typically includes a relatively large volume of an appropriate sorbent material, or a combination of sorbent materials. The sorbent material(s) adsorb odor-causing gases and other gaseous contaminants, thereby removing the contaminants from the air stream. As a point of reference, sorbent materials identified as being most effective in removing odors include charcoal or carbon, potassium permanganate, and zeolite. In fact, an extremely popular sorbent filter material is available under the trade name CPZ.TM., generally composed of 60% charcoal or carbon, 20% potassium permanganate, and 20% zeolite. By providing the sorbent material in granular form (typically stored within a rigid tray), long-term odor adsorption in commercial settings can be achieved.
With the above filtering characteristics in mind, it has been found particularly advantageous for commercial air filtration units to include a pre-filter, a primary particulate filter (e.g., HEPA filter, 95% ASHREA filter, etc.) and a sorbent material filter. The pre-filter is normally an inexpensive, low efficiency (e.g., on the order of 15% dust spot efficiency) impingement filter, such as open cell foam, employed to capture relatively large particles, thereby extending the useful life of the primary particulate filter. The primary particulate filter is positioned within the unit housing upstream of the sorbent material filter to optimize overall filtering performance. In this regard, the housing typically forms one or more slots sized to receive and maintain the filter(s).
Installation and replacement of the primary particulate filter is relatively straightforward due to the filter's construction. For example, a HEPA filter is generally formed as a continuous, relatively rigid sheet, and can be installed with relative ease.
In contrast, sorbent material filters are normally large and heavy. For most commercial applications, the sorbent material filter will include a relatively large quantity of granular sorbent material, on the order of 10-20 pounds. In fact, commercial sorbent material filters may include in excess of 50 pounds of granular sorbent material stored within a correspondingly large tray. The substantial weight associated with commercial sorbent material filters renders filter handling cumbersome at best. Especially problematic is removal of a sorbent material filter from an air filtration unit housing. As a starting point, the air filtration unit housing will, for virtually all commercial installations, be suspended above the room of interest. Thus, replacement of the sorbent material filter requires a technician to first ascend a ladder stationed below the airfiltration unit. The air intake grille and any other components located upstream of the sorbent material filter are removed and set aside. The sorbent material filter is then detached from the housing. In this regard, most commercial air filtration unit housings allow the technician to use one hand to detach the filter. Once released, the filter is no longer supported by the housing. Instead the technician must immediately and continuously support the entire filter. Unfortunately, the technician has only one free hand available for supporting the sorbent material filter, as the other hand is used to decouple the sorbent material filter from the housing. As previously described, a typical commercial sorbent material filter is normally quite heavy. As a result, the technician may experience difficulties in grasping and supporting the sorbent material filter with one hand. It is likely that the technician will inadvertently drop the sorbent material filter and/or sustain a physical injury, such as hand, neck and/or back pains.
Air-purifying devices, and in particular commercial air filtration units or modules incorporating a sorbent material filter, are extremely popular and beneficial. Certain potential drawbacks associated with filter replacement have been identified, yet remain unresolved. Therefore, a need exists for a commercial filter assembly and associated air filtration unit housing designed for convenient filter installation and replacement.